1. Field of the Invention
This invention relates to a tire forming machine which forms tires in a single stage.
2. Description of Related Art
A tire forming machine which forms tires in a single stage is provided with a forming drum like one 51 shown in FIGS. 4 and 5. The forming drum 51 is rotatably supported by a driving device (not shown) via a shaft 52 of the machine, and has a central drum portion 53 rigidly fitted to an axially central location of the drum as well as right and left drum portions 55, 54 arranged on either of the right and left sides of the central drum portion 53 and movable along the axial direction. FIG. 4 shows a state of the machine in which the right and left drum portions 55, 54 of the forming drum 51 are arranged at respective positions for setting beads (not shown).
Tires may be formed using the forming drum 51 as follows: First, various cloth-like and band-shaped tire-forming materials (not shown) are wound on the peripheral surface of the forming drum 51 as shown in FIG. 4, so as to assemble a carcass. Then, to combine these tire-forming materials along the axial direction on the forming drum 51, slender and flat support members (not shown) are once inserted into gaps S between the central drum portion 53 and the right and left drum portions 55, 54, respectively, and after the combination of the tire-forming members, the support members are removed from the respective gaps S. Next, a stitcher (not shown) is moved to stitch the carcass. The peripheral surface of the carcass is pressed to remove air remaining between the members, and at the same time the members are rigidly bonded to each other. Thereafter, known steps are carried out; i.e., beads are set to respective predetermined portions of the right and left drum portions 55, 54 by means of a supply device (not shown) and locked with some known means, and side walls of the tire-forming materials are turned up, followed by bonding a belt and a tread assembly (neither of which are shown) to the carcass. In this manner, a green tire is built.
Another tire forming method has been proposed in which, as shown in FIG. 5, the right and left drum portions 55, 54 are once moved toward the central drum portion 53 so that they come into contact with each other, and thus the forming drum 51 has a continuous surface formed thereon along the axial direction. In this state, the various cloth-like and band-shaped tire-forming materials (not shown) are wound on the peripheral surface of the forming drum 51 to assemble the carcass, and then these tire-forming materials are combined with each other on the forming drum 51 in the circumferential and axial directions. Then, the stitcher (not shown) is moved toward the forming drum 51 for stitching, and the peripheral surface of the carcass is pressed, followed by the same operations as mentioned above. Thereafter, the right and left drum portions 55, 54 are moved to open the forming drum 51, and they are returned to the bead setting positions shown in FIG. 4. Further, some known steps are carried out; i.e., the beads are set to the respective predetermined portions of the right and left drum portions 55, 54 by means of the supply device (not shown) and locked with some known means, and the side walls of the tire-forming materials are turned up, followed by bonding the belt and the tread assembly (neither of which are shown) to the carcass. In this manner, a green tire is produced.
In the conventional tire forming machines, however, when tire-forming materials are wound on the peripheral surface of the forming drum 51 under the condition of the drum shown in FIG. 4, the slender and flat support members must be inserted into the gaps S between the central drum portion 53 and the right and left drum portions 55, 54, respectively, so as to axially connect the central, right and left drum portions to each other. As a result, the workability of the machine has been poor and hence the productivity of tires cannot be improved. In addition, the workload of the insertion and removal of the support members is large and imposes a large burden on the operator. Moreover, when the gaps S are present between the central drum portion 53 and the right and left drum portions 55, 54, respectively, stitching which is done by externally pressing the entire tire-forming materials cannot be performed in a satisfactory manner. As a result, air may become confined between the layers of the tire-forming materials, causing defects, such as residual of air inside formed tires, and therefore defective tires may result.
On the other hand, when the tire-forming materials are wound on the peripheral surface of the forming drum 51 in the conventional tire forming machine as shown in FIG. 5, the central drum portion 53 is in contact with the right and left drum portions 55, 54 to form a continuous surface, and therefore combining and stitching operations of the tire-forming materials are carried out without difficulties. After the operations, however, the right and left drum portions 55, 54 must be moved to the bead setting positions to open the forming drum 51, and they must be returned to the condition shown in FIG. 4. In this case, however, the resistance force between the wound tire-forming materials and each of the right and left drum portions cannot be the same, and therefore deformation, such as entire or partial deviation or distortion, of the central line of the carcass which is obtained by assembling the tire-forming materials, may occur, resulting in defective tires. Deviations of the center may be corrected by reducing resistance on either of the right and left drum portions with air blown into the interior of the carcass when the left and right drum portions 54, 55 are moved to the set position of the beads. In reality, however, it has been difficult to maintain the central line of the carcass with precision even by this method.
It is therefor an object of the invention to provide a tire forming machine which is capable of positively eliminating center deviations, deformations, or the like of a carcass assembled from tire-forming materials, so as to maintain the quality of tires while ensuring high operating efficiency.
To attain the object, the invention provides a tire forming machine having a forming drum having a central drum portion arranged at an axially central location of the forming drum, and right and left drum portions which are arranged on either of the right and left sides of the central drum portion and which are movable in an axial direction of the forming drum, the right and left drum portions being brought into contact with the central drum portion so as to cooperatively form a continuous surface at the time of winding tire-forming materials around the forming drum for assembling a carcass, the right and left drum portions being moved to respective bead setting positions to open the forming drum after the assembly of the carcass, the tire forming machine comprising a plurality of gripping mechanisms arranged around the central drum portion of the forming drum in a movable manner for gripping an axially central portion of the carcass.
As stated above, the tire forming machine according to the invention includes the forming drum having the central drum portion arranged at the axially central location of the forming drum, and the right and left drum portions arranged on either of the right and left sides of the central drum portion movably in the axial direction, the right and left drum portions being brought into contact with the central drum portion so as to cooperatively form a continuous surface at the time of winding the tire-forming materials on the forming drum to assemble the carcass, the right and left drum portions being moved to the respective bead setting positions to open the forming drum after the assembly of the carcass. The tire forming machine comprises the gripping mechanisms arranged around the central drum portion of the forming drum in a movable manner for gripping the axially central portion of the carcass. As a result, combining and stitching operations of the tire-forming materials can be smoothly carried out. Further, center deviations or deformations of the carcass can be positively prevented while the operational efficiency is ensured. Therefore, tires with high quality can be produced and the productivity thereof can be enhanced.